Process for producing polyester resin for toner

ABSTRACT

A polyester resin for toner which is obtained through polymerization in the presence of a release agent ingredient with a melting point of 60–100° C. or a release agent ingredient comprising an alcohol component, and which has a softening temperature of 100–160° C., an acid value of 0.1–30 mgKOH/g and a glass transition temperature of 40–70° C.; a process for producing a polyester resin for toner which comprises conducting polymerization in the presence of a release agent ingredient with a melting point of 60–100° C. or a release agent ingredient comprising an alcohol component; and toner comprising the polyester resin. Toners with excellent non-offset properties and glosses are obtained.

TECHNICAL FIELD

The present invention relates to a polyester resin for toner, to aprocess for producing the polyester resin for toner and to tonercontaining it. The invention relates more particularly to a polyesterresin which is used for development of electrostatic charge images ormagnetic latent images in electrophotographic methods, electrostaticrecording methods or electrostatic printing methods, and can give tonerwith an excellent non-offset property and gloss, as well as to a processfor producing the polyester resin.

BACKGROUND ART

In methods for obtaining images by electrophotographic printing andelectrostatic charge development, an electrostatic charge image formedon a photosensitive body is developed by toner which has been previouslycharged by friction, and then fixed. Fixing systems include heat rollersystems wherein the toner image obtained by development is fixed using apressurized or heated roller, and noncontact fixing systems whereinfixing is accomplished using an electric oven or a flash of light. Inorder to carry out the process in a successful manner, the toner mustfirst hold a stable charge, and must secondly have a satisfactoryproperty of fixing onto paper. In addition, as the apparatus has aheated fixing member which increases the temperature inside theapparatus, the toner must also be resistant to blocking. Recently, withthe increased compactness of fixing members in heat roller systems,rollers are being employed that are not coated with release agents suchas silicone oil. This has produced a high demand for toners withreleasability from heat rollers, also known as a non-offset property.Also, recently, in demand are toners capable of forming glossy images,as full color electrophotographic systems come into wider use.

Toner binder resins, which have a major influence on the above-mentionedtoner properties, include polystyrene resins, styrene-acryl resins,polyester resins, epoxy resins, polyamide resins and the like, andparticular attention has been focused on polyester resins for theirability to achieve a satisfactory balance between transparency andfixing property, as well as their superior transparency and generalsuitability for full color toners.

However, toners using polyester-based resins as the binder resins tendto have a lower non-offset property than other resins such asstyrene-acryl resins, while it has also been difficult to simultaneouslyachieve sufficient gloss.

One problem, for example, has been that enhancing the non-offsetproperty of a toner by increasing the polymer weight or elasticity ofthe binder resin also lowers the gloss of the resulting image.

Moreover, it has not been possible to obtain adequate effects becauserelease agents added to toners are not readily uniformly miscible in thebinder resins.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a polyester resinfor toner which can give toner with an excellent non-offset property andgloss, as well as a process for producing the polyester resin for tonerand toner containing it.

As a result of diligent research on release agent ingredients added topolyester resins for toner, the present inventors have completed thisinvention upon discovering a solution to the aforementioned problems.

Specifically, the present invention provides a polyester resin for tonerwhich is obtained through polymerization in the presence of a releaseagent ingredient with a melting point of 60–100° C. or a release agentingredient comprising an alcohol component, and which has a softeningtemperature of 100–160° C., an acid value of 0.1–30 mgKOH/g and a glasstransition temperature of 40–70° C.

The invention further provides a process for producing a polyester resinfor toner which comprises conducting polymerization of a polyestermonomer ingredient in the presence of a release agent ingredient with amelting point of 60–100° C. or a release agent ingredient comprising analcohol component.

The invention still further provides a toner containing at least thepolyester resin for toner described above, which produces fixed imageswith a gloss of 5 to 40 degrees.

BEST MODE FOR CARRYING OUT THE INVENTION

The release agent ingredient as a constituent of the polyester resin fortoner according to the invention has a melting point in the range of60–100° C. This range is specified because a melting point of at least60° C. will tend to result in satisfactory blocking resistance of thetoner. The melting point is preferably at least 65° C. Also, a meltingpoint of up to 100° C. will tend to result in a satisfactorylow-temperature fixing property of the toner. The melting point ispreferably no higher than 95° C.

As examples of release agent ingredients with melting points of 60–100°C. there may be mentioned rice wax (m.p.: 79° C.), carnauba wax (m.p.:83° C.), paraffin wax (m.p. 40–90° C.) and bees wax (m.p.: 64° C.).

One or more of these may be selected as appropriate depending on theneed.

The release agent ingredient as a constituent of the polyester resin fortoner according to the invention may also comprise an alcohol component.By using a polyester resin comprising an alcohol component, part of thealcohol component reacts with the monomer ingredient duringpolymerization of the polyester resin, thereby enhancing thecompatibility of the polymer ingredient with the release agentingredient, allowing the dispersion size of the release agent ingredientto be smaller in the polyester resin for toner according to theinvention, and tending to result in a toner with a more satisfactorynon-offset property and gloss.

The release agent ingredient preferably has a penetration degree of nogreater than 3 at 25° C., because using a release agent with apenetration degree of no greater than 3 at 25° C. will tend to givetoner with satisfactory image stability.

As examples of release agent ingredients comprising alcohol componentsand having penetration degrees of no greater than 3 at 25° C. there maybe mentioned rice wax and carnauba wax, with carnauba wax beingparticularly preferred.

Such release agent ingredients are preferably included in the polyesterresin for toner of the invention in an amount of 0.1–10 wt %. A releaseagent ingredient content of at least 0.1 wt % will tend to give tonerwith a satisfactory non-offset property. The content is more preferablyat least 0.5 wt %. The content is also no greater than 10 wt % becausethis will tend to give toner with satisfactory gloss and imagestability. The content is more preferably no greater than 8 wt %.

According to the invention, the dispersion size of the release agentingredient in the polyester resin for toner is preferably no greaterthan 5 μm. A dispersion size of no greater than 5 μm will tend to givetoner with a satisfactory non-offset property and gloss. The dispersionsize is more preferably no greater than 3 μm.

The dispersion size of the release agent ingredient in the polyesterresin for toner is determined by melt blending the polyester resin witha twin-screw extruder controlled to an external temperature of 120° C.,sandwiching 2 g of the blended resin between polyester films, holding itfor 2 minutes while applying a load of 9.8 MPa at 180° C., and thencooling it to prepare a sample, observing and photographing thedispersion state of the release agent in the sample under a lightmicroscope, selecting the largest dispersed particle and determining thevalue of the maximum distance from the center of the dispersed particleto the outermost perimeter.

As examples of useful dicarboxylic acid components as constituents ofthe polyester resin for toner according to the invention there may bementioned terephthalic acid, isophthalic acid and their lower alkylesters. As examples of lower alkyl esters of terephthalic acid andisophthalic acid there may be mentioned dimethyl terephthalate, dimethylisophthalate, diethyl terephthalate, diethyl isophthalate, dibutylterephthalate and dibutyl isophthalate, but terephthalic acid andisophthalic acid are preferred from the standpoint of handlingproperties and cost. These dicarboxylic acids or their lower alkylesters may be used alone or in combinations of two or more.

As examples of other useful dicarboxylic acid components there may bementioned phthalic acid, sebacic acid, isodecylsuccinic acid,dodecenylsuccinic acid, maleic acid, fumaric acid, adipic acid and theirmonomethyl, monoethyl, dimethyl and diethyl esters or their acidanhydrides. Such dicarboxylic acid components will influence the basicproperties of the toner including the fixing property and blockingresistance, and may therefore be used as appropriate for the requiredperformance, in ranges that do not hinder the object of the invention.

As examples of useful glycol components as constituents of the polyesterresin for toner according to the invention there may be mentionedaromatic diol components such aspolyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.2)-polyoxyethylene-(2.0)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane,polyoxypropylene-(2.4)-2,2-bis(4-hydroxyphenyl)propane andpolyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane, which may be usedeither alone or in combinations of two or more. Aromatic diol componentshave the effect of increasing the glass transition temperature and thusyield toners with satisfactory blocking resistance. Particularlypreferred are polyoxypropylene(n)-2,2-bis(4-hydroxyphenyl)propane havinga polyoxypropylene unit number (n) of 2.1≦n≦8 andpolyoxyethylene(n)-2,2-bis(4-hydroxyphenyl)propane having apolyoxyethylene unit number (n) of 2.0≦n≦3.0.

These aromatic diol components are preferably used in amounts in therange of 10–110 mole percent and more preferably in the range of 20–100mole percent based on the total acid component.

As examples of other useful glycol components there may be mentionedethylene glycol, neopentyl glycol, propylene glycol, butanediol,polyethylene glycol, 1,2-propanediol, 1,4-butanediol, diethylene glycol,triethylene glycol, 1,4-cyclohexanedimethanol and hydrogenated bisphenolA, which may be used either alone or in combinations of two or more.

As constituents of the polyester resin for toner of the presentinvention there are preferably used tri- or higher polyvalent carboxylicacids and/or tri- or higher polyhydric alcohols.

Tri- or higher polyvalent carboxylic acids and/or tri- or higherpolyhydric alcohols are used for crosslinking or branching of thepolyester resin, and they are preferably used in an amount in the rangeof 0.1–30 mole percent based on the total acid component. This isbecause their use in an amount of at least 0.1 mole percent will tend togive toner with a satisfactory non-offset property. The amount is morepreferably at least 0.5 mole percent. Also, their use in an amount of nogreater than 30 mole percent will tend to ensure that toner withsatisfactory blocking resistance and a satisfactory fixing property isobtained. The amount is more preferably no greater than 28 mole percent.

As examples of tri- or higher polyvalent carboxylic acids there may bementioned trimellitic acid, pyromellitic acid,1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylicacid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylicacid and 1,2,7,8-octanetetracarboxylic acid or their anhydrides or loweralkyl esters, and as examples of tri- or higher polyhydric alcoholsthere may be mentioned sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan,pentaerythritol, dipentaerythritol, tripentaerythritol,1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol,2-methyl-1,2,3-propanetriol, 2-methyl-1,2,4-butanetriol,trimethylolpropane and 1,3,5-trihydroxymethylbenzene. Particularlypreferred are trimellitic acid or its anhydride, pentaerythritol andtrimethylolpropane, and these tri- or higher polyvalent carboxylic acidsand tri- or higher polyhydric alcohols may be used alone or incombinations of two or more.

According to the invention, it is important for the dicarboxylic acidcomponent and glycol component and, if necessary, a tri- or higherpolyvalent carboxylic acid and/or a tri- or higher polyhydric alcohol,to be polymerized by esterification reaction or ester-exchange reactionand condensation reaction in the presence of the aforementioned releaseagent ingredient, in order to produce the polyester resin. This willtend to yield a polyester resin for toner with a further improvednon-offset property, gloss and fixing property.

A polymerization catalyst such as titanium tetrabutoxide, dibutyltinoxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide orgermanium dioxide may be used for polymerization of the polyester resin.

The polymerization temperature for the polyester resin for toner of theinvention is preferably in the range of 180–280° C. A polymerizationtemperature of at least 180° C. will permit reaction between the releaseagent ingredient, such as carnauba wax, and the monomer ingredient forimproved compatibility between the polymer ingredient and the releaseagent ingredient, thereby tending to allow a smaller dispersion size forthe release agent ingredient in the polyester resin for toner of theinvention. The temperature is more preferably at least 200° C. Also, apolymerization temperature of no higher than 280° C. will tend toinhibit coloration of the release agent ingredient and result insatisfactory toner gloss. The temperature is more preferably no higherthan 270° C.

The polyester resin for toner of the invention preferably has asoftening temperature in the range of 100–160° C. A softeningtemperature of below 100° C. will tend to reduce the blocking resistanceof the toner. The softening temperature is more preferably at least 105°C. Also, the toner will tend to have reduced gloss if the softeningtemperature is higher than 160° C. The softening temperature is morepreferably no higher than 150° C. The polyester resin for toner of theinvention also preferably has a melting point peak in the range of60–100° C.

The polyester resin for toner of the invention also preferably has anacid value in the range of 0.1 to 30 mgKOH/g. This is because theproductivity of resins with acid values of less than 0.1 mgKOH/g tendsto be poor. The acid value is more preferably at least 0.5 mgKOH/g.Also, the image stability will tend to be reduced if the acid value isgreater than 30 mgKOH/g. The acid value is more preferably no greaterthan 25 mgKOH/g.

The polyester resin for toner of the invention preferably has a glasstransition temperature in the range of 40–70° C. This is because a glasstransition temperature of below 40° C. will tend to reduce the blockingresistance of the toner. The glass transition temperature is morepreferably at least 50° C. Also, a glass transition temperature ofhigher than 70° C. will tend to reduce the gloss of the toner. The glasstransition temperature is more preferably no higher than 65° C.

The polyester resin for toner of the invention is used as a binderresin, and coloring agents, charge control agents, flow modifiers,magnetic substances and the like may be added thereto to obtain toner.

The above-mentioned release agent or other release agents may be addedduring production of the toner if necessary, in ranges that do notimpede the object of the invention. The amount of the release agentingredient T added during production of the toner and the amount of therelease agent ingredient P used for production of the resin, i.e. duringpolymerization of the monomer, are preferably in a ratio T/P in therange of 1–100, and more preferably in the range of 0.2–80.

As additional release agents there may be mentioned polypropylene-basedwaxes, polyethylene-based waxes, synthetic ester-based waxes, paraffinwaxes, fatty acid amides, silicone-based waxes and the like.

As coloring agents to be used in the toner of the invention there may bementioned carbon black, nigrosine, aniline blue, phthalocyanine blue,phthalocyanine green, hansa yellow, rhodamine-based dyes or pigments,chrome yellow, quinacridone, benzidine yellow, rose bengal,triallylmethane-based dyes and monoazo-based, disazo-based and condensedazo-based dyes or pigments, and such dyes or pigments may be used aloneor in combinations of two or more. In the case of full color toner,benzidine yellow, monoazo-based dyes, condensed azo-based dyes and thelike may be used for yellow, quinacridone dyes, rhodamine-based dyes,monoazo-based dyes and the like may be used for magenta, andphthalocyanine blue and the like may be used for cyan. From thestandpoint of the toner color tone, image density and thermalproperties, the coloring agent is preferably used in an amount of about2–10 wt % in the toner.

As charge control agents to be used in the toner of the invention theremay be mentioned positive charge control agents such as quaternaryammonium salts and basic or electron donating organic substances, andnegative charge control agents such as metal chelates, alloy dyes andacidic or electron accepting organic substances. In the case of colortoner, it is important for the charge control agent to be colorless orlight-colored so as not to impair the color tone of the toner, and suchagents include salicylic acid or alkylsalycylic acid metal salts ormetal chelates of chromium, zinc, aluminum or the like, amide compounds,phenol compounds, and naphthol compounds. These charge control agentsare preferably used in amounts of 0.5–5 wt % in the toner. A chargecontrol agent amount of at least 0.5 wt % will ensure a sufficient levelof charge to the toner, while an amount of no greater than 5 wt % willtend to inhibit reduction in charge due to aggregation of the chargecontrol agent.

As flow modifiers or other additives to be used in the toner of theinvention there may be mentioned flow modifiers such as fine powderedsilica, alumina or titania, inorganic fine powders such as magnetite,ferrite, cerium oxide, strontium titanate and conductive titania,resistance regulators such as styrene resins and acrylic resins orlubricants, which may be used either as internal or external additives.Such additives are preferably used in amounts of 0.05–10 wt % in thetoner. Use of such additives in amounts of at least 0.05 wt % will tendto ensure an adequate effect of enhanced performance of the toner, whileamounts of no greater than 10 wt % will tend to guarantee satisfactoryimage stability of the toner.

The toner of the invention may be used as a magnetic single-ingredientdeveloping agent, a non-magnetic single-ingredient developing agent or atwo-ingredient developing agent. When used as a magneticsingle-ingredient developing agent it will contain a magnetic substance,and as examples of magnetic substances there may be mentioned magneticalloys of iron, cobalt, nickel and the like such as ferrite andmagnetite, as well as alloys containing no magnetic compounds orelements but exhibiting magnetism when subjected to appropriate heattreatment, for example, Heuslar alloys which contain manganese andcopper, such as manganese-copper-aluminum or manganese-copper-tin, orchromium dioxide and the like. Such magnetic substances are preferablyused in amounts in the range of 40–60 wt % in the toner. Using amagnesium substance in an amount of at least 40 wt % will tend to resultin toner with an adequate level of charge, while an amount of no greaterthan 60 wt % will tend to ensure that toner with a satisfactory fixingproperty is obtained. When a two-ingredient developing agent is used, itwill be in combination with a carrier. As carriers there may be usedpublicly known magnetic carriers, including magnetic substances such asiron powder, magnetite powder or ferrite powder, and such substanceshaving resin coatings on the surface. As coating resins for resin coatedcarriers there may be utilized commonly known styrene-based resins,acrylic-based resins, styrene-acrylic copolymer-based resins,silicone-based resins, modified silicone-based resins, fluorine-basedresins and mixtures of such resins.

The toner of the invention may be produced by first mixing theaforementioned polyester resin for toner with the coloring agents,charge control agent, flow modifier, magnetic substance, etc., meltblending the mixture with a twin-screw extruder or the like andsubjecting it to crude pulverization, fine pulverization andclassifying, with external addition of inorganic particles if necessary.The blending step is preferably carried out with the internaltemperature of the extruder cylinder higher than the softeningtemperature of the polyester resin. The step may also be carried outwith processing of the toner particles into spheres after finepulverization and classifying.

It is also important for the toner of the invention to have a gloss of 5to 40 degrees. Toner with a gloss of less than 5 degrees will tend tohave poor coloration and yield images with inferior gloss. The gloss ismore preferably at least 10 degrees. Also, a gloss of greater than 40degrees will tend to produce excessively strong toner coloration andresult in reduced image quality. The gloss is more preferably no greaterthan 30 degrees.

The toner of the invention also preferably has a mean particle size ofno greater than 7 μm. This is because toner with a mean particle size ofno greater than 7 μm will tend to exhibit a superior non-offset propertyand yield images with excellent gloss and resolution.

Examples of the present invention will now be explained, with theunderstanding that the invention is in no way limited thereto. Thefollowing methods were used for evaluation of the resins and tonersreferred to in the examples.

Resin Evaluation Methods

1) Softening Temperature

The temperature at which ½ of a 1.0 g sample flowed, when measured usinga CFT-500 flow tester by Shimadzu Laboratories Co., Ltd., with a 1 mmφ×10 mm nozzle, a load of 294 N (30 Kgf) and constant speed temperatureincrease at a temperature elevating rate of 3° C./min.

2) Acid Value

The value as measured by titration with a KOH solution.

3) Glass Transition Temperature

The temperature at the intersection between the chart baseline and thetangent with the endothermic curve near the glass transition, asmeasured using a differential scanning calorimeter at a temperatureelevating rate of 5° C./min.

Toner Evaluation Methods

4) Evaluation of Non-Offset Property

Printing was performed using a printer with a silicone oil coating freefixing roller, set to a roller speed of 100 mm/s and temperatureadjustable, for evaluation of the non-offset property. The offsettemperature was defined as the maximum temperature at which the tonermigrated to the fixing roller during fixing, and the non-offset propertywas judged on the following scale.

-   {circle around (∘)} (very good): offset temperature of ≧230° C.-   ◯ (good): offset temperature of ≧220° C. and <230° C.-   Δ (usable): offset temperature of ≧200° C. and <220° C.-   × (poor): offset temperature of <200° C.

5) Fixing Property

The fixing temperature was defined as the minimum temperature at whichthe toner began to fix onto paper, where the toner was fixed onto thepaper under the same conditions as for evaluation of the non-offsetproperty.

-   {circle around (∘)} (very good): fixing temperature of <120° C.-   ◯ (good): fixing temperature of ≧120° C. and <130° C.-   Δ (usable): fixing temperature of ≧130° C. and <160° C.-   × (poor): fixing temperature of ≧160° C.

6) Blocking Resistance

Approximately 5 g of toner was weighed out, placed in a sample bottleand allowed to stand for about 24 hours in a drier heated to 50° C., andthe degree of toner aggregation was evaluated as an index of theblocking resistance. The evaluation scale was as follows.

-   {circle around (∘)} (very good): Dispersion by mere inversion of    sample bottle-   ◯ (good): Dispersion by inversion of sample bottle and tapping once-   Δ (usable): Dispersion by inversion of sample bottle and tapping 2–3    times-   × (poor) Dispersion by inversion of sample bottle and tapping 4–5    times

7) Image Stability

The image stability was evaluated based on the toner charge afterprinting 10,000 sheets under the same conditions as for evaluation ofthe non-offset property.

-   {circle around (∘)} (very good): Stable charge (image density)-   ◯ (good): Slight difference between initial charge and final charge,    but no effect on image density-   Δ (usable): Change in charge (image density), but improvable with    additives-   × (poor): Large change in image density

8) Gloss

A fixer with the printing speed set to 100 mm/sec and the temperaturecontrolled to 140° C. was used to fix an image of toner onto paper withthe toner density adjusted to 0.5–2.0 mg/cm², and a PG-1 glossmeter byNippon Denshoku Industries Co., Ltd. was used to measure the gloss valueat an incident angle of 75°.

Production of Polyester Resin for Toner

The charging composition monomer ingredients and release agentingredients shown in Table 1 and 500 ppm of antimony trioxide withrespect to the total acid components were loaded into a reactor equippedwith a distillation column. The temperature was then gradually raisedwhile maintaining a stirring blade rotation rate of 120 rpm in thereactor, by heating to a reaction system temperature of 260° C., andthis temperature was sustained. Water flowed off from the reactionsystem and subsequently ceased after about 8 hours from the start ofesterification, at which time the reaction was terminated. Thetemperature of the reaction system was then lowered and kept at 230° C.and the pressure in the reactor was reduced over a period of about 40minutes to a vacuum degree of 1.0 mmHg for condensation reaction whiledistilling off the diol component from the reaction system. Theviscosity of the reaction system increased as the reaction proceeded,and the vacuum degree was increased as the viscosity increased, with thecondensation reaction being conducted until the torque of the stirringblade reached a value indicating the prescribed softening temperature.When the prescribed torque was indicated, the reaction system wasreturned to ordinary pressure, heating was terminated, the pressure wasraised with nitrogen, and the reaction product was removed over a periodof about 2 hours and gradually cooled over a period of 2 hours to obtainresins A to I.

Resins A to I obtained in this manner were subjected to compositionalanalysis by liquid-gas chromatography, confirming the resin compositionsshown in Table 1. The properties of the resins are also shown in Table1.

TABLE 1 Resin Resin A Resin B Resin C Resin D Resin E Monomer AcidTrimellitic 0.5 — 20.0 28.0 10.0 charging components anhydridecomposition (mole Terephthalic acid 99.5 100 50.0 72.0 90.0 fraction)Isophthalic acid — — 30.0 — — Dodecenylsuccinic — — — — — acid AlcoholDiol A 70.0 40.0 80.0 105 60.0 components Diol B — — — — — (moleEthylene glycol 35.0 65.0 60.0 40.0 45.0 fraction) Trimethylolpropane —5.0 — — — Resin Acid Trimellitic 0.6 — 19.9 27.9 9.8 compositioncomponents anhydride (mole Terephthalic acid 99.4 100 50.1 72.1 92.0fraction) Isophthalic acid — — 30.0 — — Alcohol Diol A 71.0 39.9 82.1102 60.0 components Diol B — — — — — (mole Ethylene glycol 30.0 60.127.9 20.0 42.0 fraction) Trimethylolpropane — 5.00 — — — Release agentCarnauba wax 8.0 5.0 2.0 0.5 1.0 ingredient 110TS — — — — — (wt %) ResinSoftening temperature (° C.) 105 120 140 150 140 properties Tg (° C.)50.0 53.0 60.0 56.0 65.0 Acid value (mgKOH/g) 10.0 5.5 8.0 25.0 7.0 Waxdispersion size (μm) 3.0 2.0 1.5 0.5 1.0 Resin Resin F Resin G Resin HResin I Charging Acid Trimellitic 20.0 16.9 20.0 — compositioncomponents anhydride (mole Terephthalic acid 50.0 42.2 50.0 100fraction) Isophthalic acid 30.0 — 30.0 — Dodecenylsuccinic — 41.0 — —acid Alcohol Diol A 80.0 48.6 80.0 70.0 components Diol B — 50.2 — —(mole Ethylene glycol 60.0 — 60.0 35.0 fraction) Trimethylolpropane — —— — Resin Acid Trimellitic 19.9 17.0 19.9 — composition componentsanhydride (mole Terephthalic acid 50.1 42.1 50.0 100 fraction)Isophthalic acid 30.0 — 30.0 — Alcohol Diol A 82.1 41.0 82.0 71.0components Diol B — 49.0 — — (mole Ethylene glycol 27.9 — 27.7 30.0fraction) Trimethylolpropane — — — — Release Carnauba wax — — — — agent110TS — — 2.0 — ingredient (wt %) Resin Softening temperature (° C.) 140140 141 104 properties Tg (° C.) 62.0 61.2 60.5 50.5 Acid value(mgKOH/g) 8.5 2.0 7.5 10.8 Wax dispersion size (μm) — — 4.0 — Diol A:Polyoxypropylene(2.3)-2,2-bis(4-hydroxyphenyl)propane Diol B:Polyoxyethylene(2.3)-2,2-bis(4-hydroxyphenyl)propane Carnauba wax:product of Toyo Petrolite, m.p.: 83° C. 110TS: Low molecular weightpolypropylene wax, YUMEX 110TS (Sanyo Chemical Industries Co., Ltd.,m.p.: 145° C.)

After melt blending 98 parts by weight of the resins containing norelease agent ingredient (Resins F, G and I) and 2 parts by weight ofcarnauba wax using a twin-screw extruder controlled to an externaltemperature of 120° C., 2 g of the resulting blend was sampled and thedispersion size of the release agent ingredient in the polyester resinwas measured by the method described above. The results were 20 μm forResin F, 12.8 μm for Resin G and 15.2 μm for Resin I.

EXAMPLE 1

Resins A to E obtained above were used to prepare toners. Each tonerincluded 89 parts by weight of the resin, 5 parts by weight ofquinacridone pigment (E02, Clariant), 5 parts by weight of carnauba wax(Toyo Petrolite) and 1 part by weight of a negatively charged chargecontrol agent (E-84, Orient Chemicals Corp.), and the ingredients weremixed for 30 minutes with a Henschel mixer. The mixture was then meltblended twice with a twin-screw extruder. The melt blending was carriedout with the internal temperature set to the softening temperature ofthe resin. Cooling after blending yielded a toner mass which was finelypulverized with a jet mill pulverizer, and the toner particle sizes wereordered with a classifier for a particle size of 5 μm. Silica (R-972,Nihon Aerosil) was added at 0.25% to the obtained fine powder andadhered thereto by mixing with a Henschel mixer, to obtain the finaltoners A to E.

Toners A to E were evaluated as toners by the evaluation methodsdescribed above. The toner evaluation results are shown in Table 2. Asseen in Table 2, the non-offset properties of Toners C and D wereexcellent, those of Toners B and E were good and that of Toner A wassomewhat inferior but acceptable for use. The image stabilities ofToners B, C and E were excellent, that of Toner A was good and that ofToner D was inferior but an acceptable level for use. The blockingresistances of Toners C and E were excellent, those of Toners B and Dwere good, and that of Toner A was inferior but an acceptable level foruse. The fixing property of Toner A was excellent, those of Toners B, Cand E were good, and that of Toner D was somewhat inferior but anacceptable level for use. All of the toners exhibited the target valuesfor gloss.

EXAMPLE 2

Toner F was produced and evaluated under the same conditions as inExample 1 except that 94 parts by weight of Resin C, 5 parts by weightof quinacridone pigment (E02, Clariant) and 1 part by weight of anegatively charged charge control agent (E-84, Orient Chemicals Corp.)were used in the toner. The results are shown in Table 2. Toner Fexhibited an excellent non-offset property, image stability and blockingresistance, and the fixing property was also excellent. It alsoexhibited a high level of gloss.

EXAMPLE 3

Toner G was produced and evaluated under the same conditions as inExample 1 except that 71.9 parts by weight of Resin A, 22.1 parts byweight of Resin C, 5 parts by weight of quinacridone pigment (E02,Clariant) and 1 part by weight of a negatively charged charge controlagent (E-84, Orient Chemicals Corp.) were used in the toner. The resultsare shown in Table 2. Toner G exhibited an excellent non-offset propertyand image stability, the blocking resistance was somewhat inferior butan acceptable level for use, and the fixing property was excellent. Italso exhibited a high level of gloss.

EXAMPLE 4

Toner H was produced and evaluated under the same conditions as inExample 1 except that 94 parts by weight of Resin A, 5 parts by weightof Pigment Yellow 180 (Clariant) and 1 part by weight of a negativelycharged charge control agent (E-84, Orient Chemicals Corp.) were used inthe toner. The results are shown in Table 2. Toner H exhibited goodimage stability, the non-offset property and blocking resistance weresomewhat inferior but acceptable levels for use, and the fixing propertywas excellent. It also exhibited a high level of gloss.

TABLE 2 Toner A B C D E F G H Non-offset Δ ◯ ⊚ ⊚ ◯ ⊚ ⊚ Δ property Imagestability ◯ ⊚ ⊚ Δ ⊚ ⊚ ⊚ ◯ Blocking Δ ◯ ⊚ ◯ ⊚ ⊚ Δ Δ resistance Fixingproperty ⊚ ◯ ◯ Δ ◯ ⊚ ⊚ ⊚ Gloss 30.0 25.0 17.0 10.0 15.0 25.0 15.0 28.0

COMPARATIVE EXAMPLE 1

Resin F was used to prepare toner under the same conditions as inExample 1, and the resulting Toner CA was also evaluated under the sameconditions as in Example 1. The results are shown in Table 3.

Toner CA exhibited an excellent non-offset property, image stability andblocking resistance, but its poor fixing property and low gloss made itunacceptable for use.

COMPARATIVE EXAMPLE 2

Toner CB was produced and evaluated under the same conditions as inExample 1, except that 88.8 parts by weight of Resin G, 7.1 parts byweight of quinacridone pigment (E02, Clariant), 2.7 parts by weight ofpolypropylene wax (VISCOL 660P, Sanyo Chemical Industries, m.p.: 145°C.) in place of carnauba wax and 1.3 parts by weight of the chargecontrol agent BONTRON S-34 (Orient Chemicals Corp.) were used in thetoner. The results are shown in Table 3. Toner CB exhibited excellentblocking resistance and the non-offset property was somewhat inferiorbut an acceptable level for use, but its inferior fixing property andimage stability and low gloss made it unacceptable for use.

In addition, 95 parts by weight of Resin G and 5 parts by weight ofpolypropylene wax (VISCOL 660P, Sanyo Chemical Industries) were meltblended with a twin-screw extruder controlled to an external temperatureof 120° C., and 2 g of the obtained melt blend mass (sample) was takenfor measurement of the dispersion size of the release agent ingredientin the polyester resin by the method described above, giving a result of15 μm.

COMPARATIVE EXAMPLE 3

Toner CC was produced and evaluated under the same conditions as inExample 1 except that 94 parts by weight of Resin H, 5 parts by weightof quinacridone pigment (E02, Clariant) and 1 part by weight of anegatively charged charge control agent (E-84, Orient Chemicals Corp.)were used in the toner. The results are shown in Table 3. Toner CCexhibited excellent blocking resistance and its non-offset property andimage stability were somewhat inferior, although acceptable levels foruse, but its inferior fixing property and low gloss made it unacceptablefor use.

COMPARATIVE EXAMPLE 4

Toner CD was produced and evaluated under the same conditions as inExample 1, except that 22.1 parts by weight of Resin G and 66.9 parts byweight of Resin I were used. The results are shown in Table 3. Toner CDexhibited a somewhat inferior non-offset property, image stability,blocking resistance and fixing property, although acceptable levels foruse, but its low gloss made it unacceptable for use.

COMPARATIVE EXAMPLE 5

Toner CE was produced and evaluated under the same conditions as inExample 1 except that 94 parts by weight of Resin I, 5 parts by weightof Pigment Yellow 180 (Clariant) and 1 part by weight of a negativelycharged charge control agent (E-84, Orient Chemicals Corp.) were used inthe toner. Toner CE exhibited a somewhat inferior fixing property andblocking resistance, although acceptable levels for use, but itsinferior non-offset property and low image stability and gloss made itunacceptable for use.

TABLE 3 Toner CA CB CC CD CE Non-offset property ⊚ Δ Δ Δ X Imagestability ⊚ X Δ Δ X Blocking resistance ⊚ ◯ ◯ Δ Δ Fixing property X X XΔ Δ Gloss 1.5 1.0 1.0 1.5 3.0

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to obtain polyesterresins for toner that exhibit an excellent non-offset property, gloss,etc. by polymerizing polyester resin monomer ingredients in the presenceof specific release agent ingredients.

1. A process for producing a polyester resin for toner, which polyesterresin comprises a tri- or higher polyvalent carboxylic acid componentand/or a tri- or higher polyhydric alcohol component at 0.1-30 molepercent based on the total acid component, and which polyester resin hasa softening temperature of 100-160° C., an acid value of 0.1-30 mgKOH/gand a glass transition temperature of 40-70° C., which process comprisesconducting polymerization of said acid and alcohol components in thepresence of a release agent ingredient comprising an alcohol component.2. The process according to claim 1, wherein the polyester comprises therelease agent ingredient at 0.1–10 wt %.
 3. The process according toclaim 1, wherein the polyester comprises an aromatic diol component at10–110 mole percent based on the total acid component.
 4. A processaccording to claim 1, wherein the release agent ingredient is carnaubawax.
 5. The process to claim 1, wherein the release agent ingredient isdispersed in the polyester resin, and the release agent ingredient has adispersion size no greater than 5 μm.